People have hidden information within documents and images for hundreds of years using a variety of methods. In recent years, the ability to copy documents and other printed matter has become much more accurate and widespread, increasing the value, within production print such as in the packaging and label space, of using hidden information for purposes such as anti-counterfeiting and track/trace of documents.
Examples of current methods include overt methods that are immediately visible, such as regular text, barcodes, holograms and sealing tapes, and covert methods are detectable, but do not immediately catch the eye, such as RFID tags, watermarks, color flecks or the like in the media, inks visible only under a UV lamp (black light) and steganography within images, and so forth. Some methods are arguably mid-way between overt and covert, such as complex guilloches or microtext. There is a need for providing information that is hidden, covert, or difficult to ascertain on printed products in an efficient manner and, preferably, with lower manpower, capital, or manufacturing costs than are found in current methods.
Another trend in the printing industry is the increasing use of variable data, for personalization or for other use cases where producing multiple unique prints that vary in some way provides a value. Variability can be applied both to the regular text and graphics on a printed piece, but also to the information hidden in overt or covert ways.